Image forming apparatus

ABSTRACT

An image forming apparatus includes an image reading portion; an image forming portion; a first casing; a second casing including a space which continuously opens to two directions perpendicular to not only the vertical direction but also each other and including a mounting portion where the first casing is mountable at a position where the space does not continuously open to the two directions; one or more supporting portion; and one or more auxiliary supporting portion. A gap is formed between itself and the other one of the first casing and the mounting portion in a state in which no load is externally exerted on the first casing, and wherein the auxiliary supporting portion contacts the other one when a load not less than a predetermined load is externally exerted on an upper portion of the first casing downward at a position deviated from the mounting portion.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an image forming apparatus such as aprinter, a facsimile machine, a copying machine or a multi-functionmachine having a plurality of functions of these machines.

As an image forming apparatus including an image reading portion, astructure in which an image reading device including the image readingportion is provided on an image forming apparatus main assemblyincluding an image forming portion has been conventionally known. Insuch a structure, a so-called in-body discharge constitution in which adischarge tray on which a recording material carrying thereon an imageformed at the image forming portion is to be discharged is provided in aspace between the image reading device and the image forming apparatusmain assembly has also been known. In the case of the in-body dischargeconstitution, in order that a user can easily take out the recordingmaterial discharged on the dispose tray, a space where the dispose trayis provided in configured so as to open to two directions toward a frontsurface and one of two side surfaces.

Such an image forming apparatus has a structure in which an imagereading portion casing constituting the image reading device andsupporting the image reading portion is provided on an image formingportion casing constituting the image forming apparatus and supportingthe image forming portion. The structure further includes a firstsupporting member provided on one of sides of the image forming portioncasing and disposed so as to be extended between a front side plate anda rear side plate and includes a second supporting member provided onthe other side of the image forming portion casing and supported by therear side plate, in a cantilever manner. The first supporting member andthe second supporting member support the image reading portion casing incooperation. In this way, the second supporting member is formed in theform of the cantilever, so that a space between the image readingportion casing and the image forming portion casing continuously opensto two directions (for example, Japanese Laid-Open Patent Application2007-293216).

However, as described above, in the case where the space between theimage reading portion casing and the image forming portion casing isconstituted so as to continuously open to the two directions, when anload is exerted on the image reading device downward on an open side ofthe space, there is a possibility that the image reading portion casingcauses distortion. Particularly, the user leans against a corner betweena front surface-side and a side surface-side opposite from another sidesurface-side where the second supporting member of the image readingdevice is disposed, and thus when a load is exerted on this cornerdownward, the image reading portion casing is liable to cause thedistortion since the second supporting member is the cantilever. Whenthe image reading portion casing causes the distortion, image readingaccuracy of the image reading portion supported by the image readingportion casing lowers. IN order to suppress the distortion, it would beconsidered that a thickness of the second supporting member is increasedor a reinforcing plate is additionally provided, but in either case, aweight and a manufacturing cost are increased.

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide an imageforming apparatus capable of reducing a degree of distortion of an imagereading portion casing.

According to an aspect of the present invention, there is provided animage forming apparatus comprising: an image reading portion for readingan image; an image forming portion for forming the image; a first casingfor supporting the image reading portion; a second casing for supportingthe image forming portion, wherein the second casing is provided belowthe first casing with respect to a vertical direction and a spacecontinuously opens to two directions perpendicular to not only thevertical direction but also each other, and wherein the second casingincludes a mounting portion where the first casing is mountable at aposition where the space does not continuously open to the twodirections; one or more supporting portion, provided on at least one ofthe first casing and the mounting portion, for supporting the firstcasing relative to the second casing; and one or more auxiliarysupporting portion, provided on one of the first casing and the mountingportion, for supporting the first casing relative to the second casing,wherein a gap is formed between itself and the other one of the firstcasing and the mounting portion in a state in which no load isexternally exerted on the first casing, and wherein the auxiliarysupporting portion contacts the other one when a load not less than apredetermined load is externally exerted on an upper portion of thefirst casing downward at a position deviated from the mounting portionfor the first casing.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an image forming apparatusaccording to an embodiment of the present invention.

FIG. 2 is a perspective view of a structure for the image formingapparatus in the embodiment as seen from a front side.

FIG. 3 is an enlarged exploded perspective view showing a portion wherean image reading portion casing is supported by an image forming portioncasing in the embodiment.

FIG. 4 is a schematic view showing a state in which a load is exerted onan image reading portion casing in an exaggerated manner in ComparisonExample.

In FIG. 5, (a) is a sectional view of a portion where the image readingportion casing is supported by the image forming portion casing in theembodiment, in which the portion is cut along a left-right direction andis viewed from a front side in the neighborhood of an auxiliarysupporting portion on a front right side, and (b) is an enlargedsectional view of the auxiliary supporting portion.

FIG. 6 is a schematic view of the portion where the image readingportion casing is supported by the image forming portion casing in theembodiment, in which the neighborhood of the portion on the front rightside is viewed from above.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described using FIGS. 1 to6. First, using FIG. 1, a general structure of an image formingapparatus in an embodiment will be described. In the followingdescription, “front” and “rear” are those with respect to a front sideand a rear side, respectively, of the image forming apparatus, and“left” and “right” are those when the image forming apparatus is seenfrom the front side. The front side of the image forming apparatus is aside where a user operates the image forming apparatus, e.g., where anoperation panel is provided or a side where the cassette foraccommodating the recording material is to be pulled out. Further, anup-down direction is that in a state in which the image formingapparatus is placed on an installation surface such as a floor.

[Image Forming Apparatus]

An image forming apparatus 1 in this embodiment employs anelectrophotographic type and a constitution in which an image readingdevice 400 a including an image reading portion 400 is provided on animage forming apparatus main assembly 300 a including an image formingportion 300. The image reading portion 400 reads an original 6, placedon an original supporting platen glass 7, by an image sensor 8 andobtains information from the original 6 as image information. The imageforming portion 301 has a so-called tandem-type structure in which aplurality of photosensitive members (image bearing members orphotosensitive drums) 10 are arranged in a travelling direction of anintermediary transfer belt (intermediary transfer member) 17.

Each of the photosensitive drums 10 is electrically charged by a charger16, and then is subjected to scanning by a laser scanner 9 (exposuredevice) on the basis of the image information read by the image readingportion 400 or image information sent from an external terminal, so thatan electrostatic latent image is formed no a surface thereof. Theelectrostatic latent image is developed as a toner image with a tonersupplied from a developing device 11. In the developing devices 11,toners of colors of yellow, magenta, cyan and black, respectively, areaccommodated. On the photosensitive drums 10, toner images of the colorsof yellow, magenta, cyan and black, respectively, are formed.

The color toner images formed on the respective photosensitive drums 10are superposedly transferred onto the intermediary transfer belt 17, sothat a superposed for color toner images are formed on the intermediarytransfer belt 17.

The toner images formed on the intermediary transfer belt 17 aretransferred, at a nip with a transfer roller 18, onto a recordingmaterial (e.g., a sheet material such as a sheet or an OPC sheet) S fedfrom a cassette 12. Specifically, sheets of the recording material S fedone by one by a feeding and separating device 13 are fed to aregistration roller pair 15 via a feeding portion 14. By theregistration roller pair 15, the recording material S is fed insynchronism with rotation of the photosensitive drums 10 and scanningtiming of the laser scanner 9.

The recording material S is fed to a fixing device 19 in a state inwhich the image is formed thereof, and then is heated and pressed by thefixing device 19, so that the image is fixed on the recording materialS. Thereafter, the recording material S on which the image is fixed isdischarged on a (paper) discharge tray 21 through a (paper) dischargingportion 20. The dispose tray 21 is provided in a space P between theimage reading device 400 a and the image forming apparatus main assembly300 a. The space P continuously opens to a front surface (side) and oneof side surfaces (left-side surface in FIG. 1) of the image formingapparatus 1 in two directions. In other words, the space P iscontinuously covered at a rear surface (side) and the other side surface(right-side surface in FIG. 1), and each of the front surface, theleft-side surface and a corner between the front surface and theleft-side surface is open. As a result, the recording materialdischarged on the discharge tray 21 can be easily taken out by the userthrough the front surface (side) or the left-side surface (side).

When the toner in each of the developing devices 11 is consumed byforming the image as described above, a developer (toner) is suppliedfrom associated one of the developer supply containers 4 a-4 d, for therespective colors, of a developer supplying portion 2 to associated oneof the developing devices 11 for the respective colors. Specifically, inthe case where a one-component developing device for carrying outdevelopment using the one-component magnetic toner is used, as thedeveloper, the one-component magnetic toner is supplied. Further, in thecase where a two-component developing device for carrying outdevelopment using a two-component developer containing a magneticcarrier and a non-magnetic toner in mixture is used, as the developer,the non-magnetic toner is supplied. Incidentally, in this case, aconstitution in which as the developer, also the magnetic carrier issupplied together with the non-magnetic toner may be employed.

The developer supplying portion 2 includes the developer supplycontainers 4 a-4 d, a driving mechanism 5, and developer supplyingdevices 3 a-3 d for supplying the developer of the respective colorsfrom the developer supply containers 4 a-4 d to the developing devices11. The developer supplying devices 3 a-3 d includes hoppers 23, supplypaths 25, and the like. The developer supply container 4 a-4 d arerotationally driven by the driving mechanism 5 when the developer isneeded, so that the developers are supplied from the developer supplycontainers 4 a-4 d to the hoppers 23. The developers discharged from thedeveloper supply containers 4 a-4 d and stored in the hoppers 23 are fedto the developing devices 11 through the supply paths 25.

The above-described constituent elements or units used from theformation of the electrostatic latent image to the formation of theimage on the recording material are supported by an image formingportion casing 100. That is, the image forming portion 300 is supportedby the image forming portion casing 100. The above-described originalsupporting platen glass 7, the image sensor 8 and the like are supportedby an image reading portion casing 800. That is, the image readingportion 400 is supported by the image reading portion casing 800.

[Structure]

A schematic constitution of a structure 500 for the image formingapparatus 1 including the image forming portion casing 100 supportingthe image forming portion 300 and the image reading portion casing 800supporting the image reading portion 400 will be described using FIG. 2.The image forming portion casing 100 is disposed under the image readingportion casing 800 and is connected with the image reading portioncasing 800 in a state in which the image reading portion casing 800 ismounted thereon. In the following, respective constitutions will bedescribed specifically.

[Image Forming Portion Casing]

The image forming portion casing 100 includes a front side plate 101, arear side plate as a second side plate, a main base 103, a right post104 and a left post 105, and the like. The image forming portion casing100 further includes a first lower right stay 106 as a stay, a secondlower right stay 113 as a second stay, a lower left stay 107, a lowerfront stay 108, an upper right stay 109, a middle left stay 110, amiddle right stay 111, an oblique stay 112, a supporting cantilever 203,and the like.

The front side plate 101 and the rear side plate 102 are providedopposed and substantially in parallel to each other via the imageforming portion 300 described above. The main base 103 not only connectsthe front side plate 101 and the rear side plate 102 but also on whichthe laser scanner 9 is mounted. The right post 104 is provided along theup-down direction and to which the front side plate 101 is fastened, andextends downwardly to the neighborhood of the installation surface whilesupporting a right end of the front side plate 101. The left post 105 isprovided along the up-down direction and to which the front side plate101 is fastened, and extends downwardly to the neighborhood of theinstallation surface while supporting a left end of the front side plate101.

The first lower right stay 106 is provided along a directionsubstantially perpendicular to the front side plate 101 so as to connectthe right post 104 and the rear side plate 102 in the neighborhood ofthe installation surface, and regulates positions of these members withrespect to a depth direction (front-rear direction) in the neighborhoodof the installation surface. The first lower right stay 106 is provided,at an inner central surface thereof with respect to a width (left-rightdirection), with a rail 106 a for guiding a cassette 12 to the imageforming apparatus main assembly 300 a in an insertable and pullable-outmanner. The width direction refers to a direction (left-right direction)which is perpendicular to the up-down direction and which is parallel tothe front side plate 101.

The second lower right stay 113 is disposed between the front side plate101 and the first lower right stay 106 with respect to the up-downdirection and is disposed toward a center side more than the first lowerright stay 106 with respect to the width direction parallel to the frontside plate 101, and connects the right post 104 and the rear side plate102. That is, the lower right stay 113 is disposed substantiallyperpendicular to the first lower right stay 106. Also at a widthwiseinner surface of such a second lower right stay 113, a rail for guidingthe cassette 12 to the image forming apparatus main assembly 300 a in aninsertable and pullable-out manner is provided.

In this embodiment, the cassette 12 includes a two-stage structure whichis omitted from FIG. 1, and a feeding path of the recording materialfrom a lower-stage cassette to an upper-stage cassette is largelydetoured in view of a load during feeding of the recording material. Forthis reason, the upper-stage cassette is disposed at a position shiftedleftward from the lower-stage cassette. Accordingly, the second lowerright stay 113 for guiding the upper-stage cassette is disposed at aposition shifted leftward relative to the first lower right stay 106 forguiding the lower-stage cassette.

The lower left stay 107 is disposed in the neighborhood of theinstallation surface so as to connect the left post 105 and the rearside plate 102 and regulates positions of these members with respect tothe depth direction in the neighborhood of the installation surface. Thelower left stay 107 is provided at a widthwise inner central surfacethereof with a rail for guiding the cassette 12 to the image formingapparatus main assembly 300 a in an insertable end pullable-out manner.The lower right stay 108 is disposed in the neighborhood of theinstallation surface so as to connect the right post 104 and the leftpost 105, and regulates positions of these posts with respect to thewidth direction in the neighborhood of the installation surface.

The upper right stay 109 is disposed so as to connect an upper end ofthe right post 104 and the rear side plate 102, and regulates positionsof these members with respect to the depth direction at the upper end.The middle left stay 110 is disposed so as to connect an upper left endportion of the front side plate 101 and the rear side plate 102, andregulates these members at the positions with respect to the depthdirection. The middle right stay 111 is disposed so as to connect anupper right peripheral portion of the front side plate 101 and the rearside plate 102, and regulates these members at the positions withrespect to the depth direction. The oblique stay 112 is disposed so asto connect an upper left end portion of the front side plate 101 and arear portion of the middle right stay 111, and suppresses distortion ofthe image forming portion casing 100.

The supporting cantilever 203 is an open-side plate member which issupported at one end thereof by an upper left portion of the rear sideplate 102 and which extends toward the front side at the other endthereof as shown in FIG. 3. Further, as shown in FIG. 3, fixing plateportions 201, 202 are fixed to the upper right stay 109 at a right-sidesurface of the upper right stay 109. Each of the fixing plate portions201, 202 is formed by being bent so as to project upward from the lowerright stay 109.

The thus-constituted image forming portion casing 100 is provided withthe space P which continuously opens into two directions not onlyperpendicular to the up-down direction but also perpendicular to eachother. As described above, in order to easily take out the recordingmaterial discharged on the discharge tray 21 disposed in the space Pbetween the image reading device 400 a and the image forming apparatusmain assembly 300 a, the space P continuously opens to the front surfaceand the left-side surface in the two directions. For this reason, aspace where there is no portion supported by the image forming portioncasing 100 is formed under the image reading portion casing 800 on afront left side. Here, the two directions toward the front surface andthe left-side surface are two directions (front direction and leftdirection), distort each other, of four directions (front direction,rear direction, left direction and right direction) which hare not onlydistort the up-down direction of the image forming portion casing 100but also perpendicular to each other.

In this embodiment, in order to realize such a constitution, an upperend position of the left post 105 is made lower than an upper endposition of the right post 104. In other words, the upper end of theleft post 105 is extended to a lower end of the above-described P anddoes not reach the image reading portion casing 800. On the other hand,the upper end of the right post 104 is extended to an upper end of thespace P and reaches the neighborhood of a lower end of the image readingportion casing 800. Further, the front side plate 101 is disposedbetween the left post 105 and the right post 104 in a range from theupper end to an intermediary position of the left post 105, and themiddle left stay 110 is disposed between an upper end position of theleft post 105 and the rear side plate 102. As a result, the imageforming portion casing 100 is provided with the space P whichcontinuously opens into the two directions toward the front surface andthe left-side surface. Incidentally, in FIG. 2, the space P of the imageforming portion casing 100 also opens to the right-side surface, butbetween the right-side surface of the front surface of the space P, theright post 104 exists, and therefore two directions toward theright-side surface and the front surface are not continuous.

[Image Reading Portion Casing]

The image reading portion casing 800 is, as shown in FIG. 2, formed in asubstantially box-like shape and includes a bottom plate portion 810, afront wall portion 811, a rear wall portion 812, a right wall portion813, a left wall portion 814, and the like. For this reason, the imagereading portion casing 800 has a substantially rectangular shape whenviewed from one of the up-down direction. The front wall portion 811,the rear wall portion 812, the right wall portion 813 and the left wallportion 814 wall portions formed so as to raise from a front side, arear side, a right side and a left side, respectively, of the bottomplate portion 810 (in the up-down direction), and free ends thereof arebent toward the inside. The thus-constituted image reading portioncasing 800 is disposed on the image forming portion casing 100 describedbelow.

[Connection Between Image Reading Portion Casing and Image FormingPortion Casing]

Connection between the image reading portion casing 800 and the imageforming portion casing 100 will be described using FIG. 3. FIG. 3 is aperspective view showing a separated state between the image formingportion casing 100 and the image reading portion casing 800. In thisembodiment, the image forming portion casing 100 includes the upperright stay 109 and a bent plate portion 102 a which are used as amounting portion capable of mounting the image reading portion casing800. The upper right stay 109 and the bent plate portion 102 a reprovided at positions where the above-described space P does notcontinuously open into the two directions, i.e., on the right-side andthe rear surface, respectively.

That is, at an upper right portion of the image forming portion casing100, the upper right stay 109 is disposed so as to connect the upper endof the right post 104 with the rear side plate 102, so that the imagereading portion casing 800 is mountable on the upper surface of theupper right stay 109. Further, at an upper end portion of the rear sideplate 102 and at a position which is substantially same height (level)as the upper surface of the upper right stay 109, the bent plate portion102 a bent from the upper end of the rear side plate 102 toward thefront side is formed, so that the image reading portion casing 800 ismountable on the upper surface of the bent plate portion 102 a. On theother hand, at the upper left portion of the image forming portioncasing 100, as described above, the supporting cantilever 23 supportedby the rear side plate 102 at one end thereof is disposed, but the imagereading portion casing 800 is not mounted on the supporting cantilever203. At a position which is substantially the same height as the upperright stay 109 of the image forming portion casing 100 and on the leftside of the upper right stay 109, no member is disposed, and thereforeat the portion, there is no portion on which the image reading portioncasing 800 is mountable. Accordingly, the image reading portion casing800 is mounted on the right side and the rear side where the space Pdoes not open into the two directions.

As described above, the image reading portion casing 800 has thesubstantially rectangular shape as seen in one of the up-down direction,and the upper right stay 109 and the bent plate portion 102 a as themounting portion are positioned under mutually crossing two sides of theimage reading portion casing 800. That is, the right side and the rearside of the substantially rectangular image reading portion casing 800are mounted on the upper right stay 109 and the bent plate portion 102a, respectively. In the neighborhood of these two sides of the bottomplate portion 810 of the image reading portion casing 800, supportingportions 801, 802, 803 supporting the image reading portion casing 800relative to the image forming portion casing 100 are provided. Thesupporting portions 801-803 support the image reading portion casing 800relative to the image forming portion casing 100 irrespective of anexternal load on the image reading portion casing 800.

In the case of this embodiment, the three supporting portions 801-803are provided, so that the image reading portion casing 800 is supportedby the image forming portion casing 100 at three positions (three-pointsupporting). The supporting portions 801, 802, 803 for supporting theimage reading portion casing 800 relative to the image forming portioncasing 100 are formed so as to project downward at the three positionsin the neighborhood of the above-described two sides of the bottom plateportion 810. That is, the supporting portion 801 is formed in theneighborhood of a corner between the side and the rear side of thebottom plate portion 810, the supporting portion 802 is formed in theneighborhood of a corner between the right side and the rear side of thebottom plate portion 810, and the supporting portion 803 is formed inthe neighborhood of a corner between the right side and the front sideof the bottom plate portion 810. Each of the supporting portions 801-803is, as shown in (a) of FIG. 5, formed by being subjected to drawing soas to be projected downward at an associated position of the bottomplate portion 810. In (a) of FIG. 5, only the supporting portion 803 isshown, but the supporting portions 801, 802 are similarly formed.

In this embodiment, as described above, the supporting portions 801-803are formed in the neighborhood of the two sides connecting the threecorners, other than a front left corner, of the substantiallyrectangular image reading portion casing 800, i.e., in the neighborhoodof the right side and the rear side of the image reading portion casing800. Further, the supporting portions 801-803 are discharged in theneighborhood of the above-described three corners, i.e., those otherthan the front left corner. When the image reading portion casing 800 ismounted on the image forming portion casing 100, the supporting portions801-803 contacts the upper surfaces of the upper right stay 109 and thebent plate portion 102 a, whereby the image reading portion casing 800is supported by the image forming portion casing 100. Specifically, thesupporting portion 801 contacts the upper surface of the bent plateportion 102 a, and the supporting portions 802, 803 contact the uppersurface of the upper right stay 109. As a result, the image readingportion casing 800 is positioned with respect to the up-down direction.

As described above, in the state in which the image reading portioncasing 800 is mounted on the image forming portion casing 100, the imagereading portion casing 800 is fixed on the image forming portion casing100. Specifically, in the state in which the image reading portioncasing 800 is mounted on the image forming portion casing 100, the imagereading portion casing 800 is sandwiched between the fixing plateportions 201, 202 fixed on the upper right stay 109 and the supportingcantilever 203 supported on the rear side plate 102 at the upper leftportion in an open-side state. Then, the image reading portion casing800 is fastened to the fixing plate portions 201, 202 with screw or thelike on the right side and is fastened to the supporting cantilever withscrews or the like on the left side. As a result, not only the imagereading portion casing 800 is positioned with respect to a directionperpendicular to the up-down direction but also the image readingportion casing 800 is fixed on the image forming portion casing 100.

In this way, the image reading portion casing 800 is supported at thethree positions of the upper surfaces (installation surface) of theupper right stay 109 and the bent plate portion 102 a, so that not onlythe image reading portion casing 800 can be stably supported but alsodistortion can be suppressed. Further, in this embodiment, as describedlater, the upper right stay 109 and an auxiliary supporting portion 109a are provided in a state in which a predetermined gap (spacing) withthe image reading portion casing 800 is formed in a state in which theimage reading portion casing 800 is mounted on the image forming portioncasing 100.

Comparison Example

Comparison Example in which the auxiliary supporting portion 109 a isnot provided in the above-described constitution will be described usingFIG. 4. In the case of Comparison Example, when a load is externallyexerted an upper portion of the image reading portion casing 800downward at a position deviated (away) from the portion where the imagereading portion casing 800 is mounted on the image forming portioncasing 100, as indicated by a broken line in an exaggerated manner,there is a possibility that the image reading portion casing 800 isdistorted. For example, there is a possibility that the load is exertedas described above during transportation of the image forming apparatusor when a user leans against the image reading device. Particularly, atan upper portion of the portion of the image reading portion casing 800where the space P continuously opens into the two directions, i.e., atthe front left corner of the image reading portion casing 800, in thecase where the load is exerted on the portion downward, a force oftwisting the image reading portion casing 800 so that the front leftportion of the image reading portion casing 800 lowers generates. Bythis twisting, there is a possibility that the image reading portioncasing 800 is plastically deformed to cause distortion.

[Auxiliary Supporting Portion]

Therefore, in this embodiment, as shown in FIGS. 5 and 6, by providingthe auxiliary supporting portion 109 a, the above-described distortionis suppressed. The auxiliary supporting portion 109 a is provided on theupper surface of the upper right stay 109 as the mounting portion andforms a gap (spacing) with a part of the image reading portion casing800 in a state in which the load is not externally exerted on the imagereading portion casing 800. On the other hand, the auxiliary supportingportion 109 a contacts the part of the image reading portion casing 800in the case where a load not less than a predetermined load isexternally exerted on the upper portion of the image reading portioncasing 800 downward at the position deviated from the upper right stay109 and the bent plate portion 102 a. Thus, the image reading portioncasing 800 is supported by the image forming portion casing 100.

Specifically, the auxiliary supporting portion 109 a is, as shown in (a)of FIG. 5, provided on a side toward the space P move than thesupporting portion 803 in a state in which a predetermined gap T isformed between itself and the bottom plate portion 810 of the imagereading portion casing 800. The auxiliary supporting portion 109 a isformed by being subjected to drawing so as to project upward at a partof the upper right stay 109, toward the space P, which is formed bysubjecting a metal plate to bending. In addition, as shown in (b) ofFIG. 5, the predetermined T is formed between a top of the auxiliarysupporting portion 109 a and the lower surface of the bottom plateportion 810.

The predetermined gap T is set so as to be smaller than a deformationamount in which the image reading portion casing 800 is plasticallydeformed in the case where the auxiliary supporting portion 109 a is notprovided when the predetermined load is externally exerted on the frontleft corner of the image reading portion casing 800 downward. Here, thefront left corner of the image reading portion casing corresponds to theupper portion of the portion where the space P continuously opens intothe two directions. The predetermined load is appropriately setdepending on a structure of the image reading portion casing 800 or arelationship between a position of the auxiliary supporting portion 109a and positions of the supporting portions 801-803, but is 49N (about 5kgf) or more in this embodiment. An upper limit of the predeterminedload also depends on strength of the auxiliary supporting portion 109 aand can be appropriately set, but is 400N (about 40 kgf or about 41 kgf)in this embodiment. That is, in this embodiment, the predetermined loadis 49N or more and 400N or less.

Also the predetermined gap T is appropriately set depending on thestructure of the image reading portion casing 800 or the relationshipbetween the position of the auxiliary supporting portion 109 a and thepositions of the supporting portions 801-803 so as to satisfy theabove-described condition. In either case, the auxiliary supportingportion 109 a forms the predetermined gap T with the lower surface ofthe bottom plate portion 810 in the state in which the load is notexternally exerted on the image reading portion casing 800. In the casewhere the load of 49N or more is externally exerted on the front leftcorner of the image reading portion casing 800, the auxiliary supportingportion 109 a contacts the lower surface of the bottom plate portion810, so that the image reading portion casing 800 is supported by theimage forming portion casing 100 to be prevented from being plasticallydeformed.

The position where the auxiliary supporting portion 109 a is provided ison the space P side more than any one of the supporting portions801-803. This is because in the case where the downward load is exertedon the upper side of the space P of the image reading portion casing800, the image reading portion casing 800 on the space P side is likelyto deform with the supporting portions 801-803 as a fulcrum so as tolower. For this reason, such deformation can be suppressed efficientlyby providing the auxiliary supporting portion 109 a on the space P sidemore than any one of the supporting portions 801-803. Particularly, theposition where the auxiliary supporting portion 109 a is provided maypreferably be disposed in the neighborhood of the supporting portions801, 803 disposed close to the front left corner. In this embodiment, onthe rear left side where the supporting portion 801 is provided, theimage reading portion casing is fixed on the supporting cantilever 203,and therefore at this portion, the deformation of the image readingportion casing 800 is suppressed by the supporting cantilever 203.Accordingly, the auxiliary supporting portion 109 a is provided not onlyin the neighborhood of the front right-side supporting portion 803 butalso on the space P side more than this supporting portion 803.Incidentally, a similar auxiliary supporting portion may also beprovided on the supporting portion 802 side.

Further, the auxiliary supporting portion 109 a is provided below thefront wall portion 811 as the wall portion formed along the up-downdirection of the image reading portion casing 800 as shown in FIG. 6. Asa result, in the case where the load as described above is exerted onthe image reading portion casing 800, the auxiliary supporting portion109 a contacts a lower portion or the neighborhood of the front wallportion 811 of the bottom plate portion 810. The front wall portion 811is formed along the up-down direction, and therefore the rigidityagainst the up-down direction is high. For this reason, the auxiliarysupporting portion 109 a is provided at this position, so thatdistortion of the image reading portion casing 800 in the case where theload is exerted on the image reading portion casing 800 can beefficiently suppressed.

As described above, in this embodiment, even in such a constitution thatthe space P between the image reading portion casing 800 and the imageforming portion casing 100 continuously opens into the two directions,the distortion of the image reading portion casing 800 can be caused toless generate. That is, in the case of this embodiment, in addition tothe supporting portions 801-803 supporting the image reading portioncasing 800 relative to the image forming portion casing 100, theauxiliary supporting portion 109 a is provided via the predetermined gapT between itself and the image reading portion casing 800. For thisreason, in the case where the load of not less than the loadpredetermined is externally exerted on the image reading portion casing800, the image reading portion casing 800 contacts the auxiliarysupporting portion 109 a, so that the distortion of the image readingportion casing 800 can be caused to less generate. As a result, it ispossible to suppress a phenomenon that the image reading portion casing800 causes the distortion to lower accuracy of image reading by theimage reading portion casing 800. Further, the distortion of the imagereading portion casing 800 can be suppressed without increasing thethickness of the supporting cantilever 203 or without separatelyproviding the reinforcing member, and therefore it is possible tosuppress increases in weight and manufacturing cost.

Further, in the case of this embodiment, the image reading portioncasing 800 and the auxiliary supporting portion 109 a are in non-contactwith each other in the state in which the load is not exerted on theimage reading portion casing 800 or in the case where the load less thanthe predetermined load is exerted on the image reading portion casing800. For this reason, in such a normal state, the image reading portioncasing 800 is supported at three positions by the image forming portioncasing 100. For example, in the case where the image reading portioncasing 800 is supported at four positions, there is a possibility thatone or more supporting portion which does not contact the mountingsurface exists due to tolerance of each of members, e.g., a differencein projection amount between the respective supporting portions orparallelism of the mounting surface for the upper right stay 109 and thebent plate portion 102 a. In this case, there is a possibility that theimage reading portion casing 800 causes twisting. On the other hand, inthis embodiment, the auxiliary supporting portion 109 a contacts theimage reading portion casing 800 in the case where the load not lessthan the predetermined load is exerted on the image reading portioncasing 800, and therefore in the above-described normal state, the imagereading portion casing 800 is prevented from being supported at the fourpositions. As a result, in the normal state, the image reading portioncasing 800 is stably supported by the image forming portion casing 100,so that generation of the twisting can be suppressed.

Other Embodiments

In the above-described embodiment, the three supporting portions forsupporting the image reading portion casing 800 relative to the imageforming portion casing 100 are provided (three-point supporting), butthe supporting portion may only be required to be provided at oneposition. However, in the case where the image reading portion casing800 is intended to be supported at the four or more positions, there isa possibility of existence of the supporting portion which does notcontact the mounting surface due to the tolerance of each of themembers. In this case, the image reading portion casing 800 causes thetwisting. For this reason, the image reading portion casing 800 maypreferably be supported at less position to the possible extent. On theother hand, when the single supporting portion for supporting the imagereading portion casing 800 is provided, the image reading portion casing800 becomes unstable. For this reason, the number of the supportingportions for supporting the image reading portion casing 800 maypreferably be two or three, more preferably be three.

The above-described supporting portion includes not only the case wherethe contact portion such as a projection contacting the mounting surfaceis one at one position but also the case where the contact portion istwo at one position. For example, a single supporting portion isconstituted by disposing two contact portions with a small interval.Here, in a constitution including three supporting portions, when anyone of the supporting portions has two contact portions with a largeinterval, the constitution is not changed from a 4-point-supportingconstitution in the end. For this reason, in this case, the intervalbetween the two contact portions is made small, e.g., made ⅓ or less ofa length one side in the neighborhood of the bottom plate portion 810where the supporting portions are provided.

In the above-described embodiment, the supporting portions are providedon the image reading portion casing 800, but may also be provided on theimage forming portion casing 100 or on both of the image reading portioncasing 800 and the image forming portion casing 100. For example, thesupporting portion 801 is post on the image reading portion casing 800side, and the supporting portions 802, 803 are disposed or the imageforming portion casing 100 side. In summary, the supporting portion mayonly be required to be disposed at least at any position of the mountingportion between the image reading portion casing 800 and the imageforming portion casing 100.

Further, in the above-described embodiment, the single auxiliarysupporting portion is provided on the upper surface of the upper rightstay 109 as the mounting portion of the image forming portion casing100, but may also be provided on the image reading portion casing 800. Aplurality of auxiliary supporting portions may also be provided oneither one or both of the image reading portion casing 800 and the imageforming portion casing 100. For example, one auxiliary supportingportion is provided on the image reading portion casing 800 side in theneighborhood of the supporting portion 801 and another auxiliarysupporting portion is provided on the image forming portion casing 100side in the neighborhood of the supporting portion 803. In either case,in the case where the auxiliary supporting portion is provided on one ofthe image reading portion casing 800 and the image forming portioncasing 100 at the mounting portion, a gap is provided at the mountingportion in a state in which the load not less than the predeterminedload is not exerted on the image reading portion casing 800.

According to the present invention, even in such a constitution that thespace between the image reading portion casing and the image formingportion casing continuously opens into the two directions, thedistortion of the image reading portion casing can be caused to lessgenerate while suppressing the increases in weight and manufacturingcost.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2015-007944 filed on Jan. 19, 2015, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image forming apparatus comprising: an image reading portion for reading an image; an image forming portion for forming the image; a first casing for supporting said image reading portion; a second casing for supporting said image forming portion, wherein said second casing is provided below said first casing with respect to a vertical direction and a space continuously opens to two directions perpendicular to not only the vertical direction but also each other, and wherein said second casing includes a mounting portion where said first casing is mountable at a position where the space does not continuously open to the two directions; one or more supporting portion, provided on at least one of said first casing and said mounting portion, for supporting said first casing relative to said second casing; and one or more auxiliary supporting portion, provided on one of said first casing and said mounting portion, for supporting said first casing relative to said second casing, wherein a gap is formed between itself and the other one of said first casing and said mounting portion in a state in which no load is externally exerted on said first casing, and wherein said auxiliary supporting portion contacts the other one when a load not less than a predetermined load is externally exerted on an upper portion of said first casing downward at a position deviated from said mounting portion for said first casing.
 2. An image forming apparatus according to claim 1, wherein said predetermined load is 49N when the load is exerted on a portion above a portion of said first casing where the two directions to which the space opens are continuous.
 3. An image forming apparatus comprising: an image reading portion for reading an image; an image forming portion for forming the image; a first casing for supporting said image reading portion; a second casing for supporting said image forming portion, wherein said second casing is provided below said first casing with respect to a vertical direction and a space continuously opens to two directions perpendicular to not only the vertical direction but also each other, and wherein said second casing includes a mounting portion where said first casing is mountable at a position where the space does not continuously open to the two directions; one or more supporting portion, provided on at least one of said first casing and said mounting portion, for supporting said first casing relative to said second casing; and one or more auxiliary supporting portion, provided on one of said second casing and said mounting portion on a side toward the space move than said one or more supporting portion in a state in which a predetermined gap is formed between itself and the other one of said second casing and said mounting portion.
 4. An image forming apparatus according to claim 3, wherein the predetermined gap is set so as to be smaller than a deformation amount in which said first casing for supporting said image reading portion is plastically deformed when there is no auxiliary supporting portion in a case where a load of 49N or more and 400N or less is externally extended downward on an upper portion of a portion of said first casing where two directions to which the space opens are continuous.
 5. An image forming apparatus according to claim 1, wherein said first casing has a substantially rectangular shape as seen from one side of the vertical direction, and wherein said mounting portion is positioned below two sides, of said first casing, crossing each other.
 6. An image forming apparatus according to claim 3, wherein said first casing has a substantially rectangular shape as seen from one side of the vertical direction, and wherein said mounting portion is positioned below two sides, of said first casing, crossing each other.
 7. An image forming apparatus according to claim 1, wherein 3 supporting portions are provided.
 8. An image forming apparatus according to claim 3, wherein 3 supporting portions are provided.
 9. An image forming apparatus according to claim 1, wherein said first casing includes a wall portion formed along the vertical direction, and wherein said auxiliary supporting portion is provided below said wall portion with respect to the vertical direction.
 10. An image forming apparatus according to claim 3, wherein said first casing includes a wall portion formed along the vertical direction, and wherein said auxiliary supporting portion is provided below said wall portion with respect to the vertical direction. 